tree roots damage swimming pool

maikhanh

Hello,

So here is the big picture. The swimming pool is in the middle of the garden. Around it are several birch trees, one melaleuca (about 30' and 5 ft away from the pool), one fruitless pear tree, and one liquid amber.

Within the past couple months, the owner has noticed that his pool deck and the coping has been separated gradually, and finally he noticed some tree roots coming out between the two.

I have done some research but can't find out which tree would have cause this damage. Would it be the Melaleuca? The soil at the site is expansive. And it is in Southern California. How do I find out which tree the roots belong to?

Thank you,

treeshaveneeds

A picture would help a lot. But you could also take some samples of the root. Root tissue is structured differently from stem wood, but there are similarities. With trees as diverse as pear and birch and melaleuca, you should be able to tell the difference. There are pictures available for the stem wood of many species. Colour may also help - Birch tends to be creamy white, Pear a medium brown, the folks from Oz could help you with Melaleuca, and the smell of the wood is usually quite distinctive - Melaleuca may be very obvious this way.
I presume the roots are not growing in a location where there is water drainage. Is the pool chlorinated, oxygenated, treated with salt, UV? I am fairly sure birch could not stand chlorination, and I rather doubt pear could.

Hope this gives you some ideas. A pic would REALLY, REALLY HELP.

Eric Frei

The coping on many pools I've seen pops off anyway when it gets old, it's often like cement render over the top of the concrete pool.

When it lifts up the fine roots get in there (small gap) and it can be moist. As the roots expand exerting pressure between the two surfaces so the coping lifts more.

I would personally say that the coping needs fixing anyway.

But the deck bit, I'd have to see pictures of that.

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maikhanh

Here are the photos of the root. I hope someone be able to tell what kind of tree it is. I tried to smell the root, but clearly couldn't tell which tree in the garden.

Thanks!!

Attached Thumbnails

   

treeshaveneeds

This looks like the tree roots are merely growing in a void. I really doubt they caused the separation.

Eric Frei

Yep, I knew it.

That is not the coping anyway, the coping is the tiled/paved part directly on top of the pool.

That path around the pool is just poured concrete on top of existing soil, the existing soil moves and so does the concrete that sits on it .... very common and typical.

Even with no trees around I see that a lot.

Also looks like the pool has sunk, likely from the weight of the water. Imagine a bucket full of wet clay, you step in it and as you push your foot down the clay rises around it.

The tell tale sign of the pool sinking is the soil right next to it pushing up and then the concrete with it. It also always tends to push out sideways a little.

In this thread you can read the story of a large case where a building has done the same.

Twin topped - peaked hoop pine | Suggestions | Subsidence?

Here's a picture from it. The technical term is that the soil has lost bearing capacity, sometimes on reactive clays they put piers, poles etc below the pool.

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maikhanh

Thanks for your help!! So you guys are saying the separation between the concrete deck and the coping was caused by the expansive soil lifting up? The tree root itself has nothing to do with this?

We checked the water level in the swimming pool, there is no crack on the shell and the water level remained the same throughout the whole pool.

Thanks for the info, i will check out the site again.

khanh

maikhanh

Oh one more thing.. Would anyone be able to tell me whether these trees have invasive root system or not?

some say birch root is not a problem, some say it might be. I doubt that the pear tree (7 feet away) and pepper tree (12 feet away) would cause any root problem, even though they are the closest ones to the root in the photos. What about Melaleuca?

if there were tree stumps cut down, do their roots still survive? if so, is there an average period which they last?

Thank you,

Khanh

Eric Frei

You'll need to get a geotech guy out and an arborist out and an engineer out to all argue.

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treeshaveneeds

Birch roots not likely to be a problem. Unfamiliar with Melaleuca, but I have heard they can be invasive and aggressive. Most trees like this will sprout from the roots especially if the roots can survive on their own. Digging out the stumps 12-18 inches deep usually severs all roots from the core, and each root has to make it on its own. Aggressive trees can do it; regular trees do not.

treeshaveneeds

That is what Ekka is saying - expansive soil is creating the problem. And realistically, could a little root do all the damage that is seen here? There is a lot of force at play here, and tree roots -- despite all the arguments -- are not going to move a huge slab of concrete sideways, the way it has happened. Water in clay has that ability; a small tree root does not. The root just happens to be visible, and everyone jumps on what is visible, instead of thinking thru the logistics logically.

Eric Frei

If the entire pool sinks and remains level of course the water level remains the same inside the pool.

Have a look at that 3 story block of units, it sank almost square and parallel, then look at the concrete around it, familiar? Of course.

Look at your second picture, note the step and the lift/sink compared to the pool.

Is your filter sucking air (bubbles are seen)? Often the pipes crack around the skimmer box and air is easier to suck than water.

The tree roots are exploiting the crevices and cracks, likely because they contain more moisture.

Roots of melaleucas can be invasive and aggressive, but once disconnected from they stump they do die. Root barriers can be installed so roots do not go to the pool.

In the hoop pine thread I gave a link to the body corporate and engineers were blaming the large hoop pine tree for the subsidence, in actual fact the tree was helping acting as a big pump getting rid of excess water, removal of the tree would make the problem worse.

Clay soils can also contract when dry, and buildings also sink (called subsidence). So did it sink because the soil was too dry or too wet? This is where engineers and geotechs are required but there is tell tale signs as seen in the pictures.

Engineers do not like trees because they influence soil moisture levels, engineers like things static with little change. Here's the clincher, soil moisture levels are rarely influenced by trees deeper than 1.5m, and I know your pool is deeper than that so I doubt the trees had much to do with it.

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treeshaveneeds

Good arguments Ekka. Right on!

jmskrmr

In any case, out of the trees you mentioned, the liquid amber has by far the largest and most invasive root system. That is most likly the one you are seeing.